The present invention relates to an instrument panel for an air bag, which stores an air bag for a passenger seat in particular among vehicle air bags, in a folded state at the inside thereof and which cleaves so as to deploy the air bag in front of a passenger as the air bag inflates in emergency.
An air bag system for constraining a passenger by being inflated when a vehicle collides is disposed at the inside of an instrument panel in many recent vehicles.
While a cleaving section for deloying the air bag within the car room is provided in the instrument panel of this type, the quality of appearance of the instrument panel is liable to degrade in general when the cleaving performance is to be enhanced. This is because the cleaving section is created by embrittling the part of the instrument panel corresponding to an air bag deployment section. Therefore, it is required to reconcile and have both the cleaving performance and the quality of appearance of the instrument panel for an air bag.
Some of such instrument panels have a cushion layer made of foam resin. Such instrument panels include (1) one in which a skin member, a door member and the cushion layer are formed in a body by injecting and foaming the foam material between the skin member and the door member having a single-layer structure, (2) and another one in which a skin member having a double-layer structure formed by molding a skin layer and the cushion layer in a body in advance is formed in a body with the door member by injection-molding synthetic resin, thus forming the door member on the back of the skin member. The difference of those structures originates mainly from the difference of the foam resins forming the cushion layer, i.e. polyurethane foam resin is used usually for the former and polyolefine foam resin is used usually for the latter.
In the panel using the skin member having the single-layer structure, the cleaving section, for example, is created by providing a groove by means of a high-frequency welder or the like on the back of the skin member at the part corresponding to the air bag deployment section.
While a relatively hard type of the vinyl chloride resins has been used for such a skin member having the single-layer structure, and thus the above-mentioned cleavage was relatively readily achieved in the past, some of the skin members are made of soft PVC (poly-vinyl chloride) or TPO (styrene or olefinic thermoplastic elastomer) recently, thus causing a problem that the cleaving section cleaves less readily as compared to the past ones because such material has extensibility and flexibility more than the above-mentioned material.
Further, although the cleavage may be achieved more readily by thinning the thickness of the cleaving section, there has been a problem that the moldability of the thin part and the durability of the product drop due to the characteristics of the PVC and TPO, thus damaging the quality of appearance thereof.
Meanwhile, in the panel using the skin member having the above-mentioned double-layer structure, as shown for example in FIG. 14, a cleaving section 105 is created by molding a door member 104 made of thermoplastic resin by means of injection molding on the back of and in a body with a skin member 103 formed by disposing a cushion layer 101 made of foam resin and a barrier layer 102 made of soft resin on the back of a skin layer 100 and by cutting the part of the door member 104 and the skin member 103 corresponding to the air bag develoyment section into the shape as shown in the figure by means of ultrasonic or a high-frequency laser.
Because the cleaving section 105 is created after the molding, i.e. after producing the instrument panel, the door member 104 is disconnected in creating the cleaving section 105. Therefore, there has been a problem that because the rigidity of the part corresponding to the cleaving section 105 is low during normal use, the skin layer 100 is dented or wrinkled locally, thus damaging the quality of appearance as stress is concentrated on the thin part of the skin member 103 where the rigidity is low when force is applied by touching the instrument panel for example.
Further, it requires a cumbersome post-processing of creating the cleaving section 105 after the production of the instrument panel. It still further requires highly advanced technology keeping the depth of the cut for creating the cleaving section 105 constant and in controlling the thickness of the panel at the part corresponding to the cleaving section 105. These have caused an increase in production cost.